For years now, National Széchényi Library and libraries beyond the borders of Hungary, especially Transylvanian libraries, have successfully cooperated in the digitization of Hungary-related printed heritage. Within the framework of cooperation, staff members of Transylvanian libraries select and digitize valuable publications of their collection, which can be regarded as public domain and which they hold in high esteem. Then these documents are sent to NSZL which, in turn, would service them in its online collections. In the course of work, several gap-filling publications have been sent to the Hungarian national library: publications the original print version of which was missing from the stock of NSZL.
Currently, the most active cooperating partner is Csíkszereda-based Kájoni János Library of Hargitha County that has sent digitized documents to National Széchényi Library since 2009. NSZL services books in Hungarian Electronic Library (Hungarian abbreviation: MEK) and periodicals in EPA. As a result of several years of successful cooperation, the Hungarian national library currently services nearly 300 books and 15 periodicals received from Csíkszereda. Antecedent and initiator of cooperation in Székely Land was András Lajos Róth, librarian of Székelyudvarhely-based Scientifical Library of the Haáz Rezső Museum, who was also active in Hungarian circles. It was him who, in 2006, started digitizing the stock of his library and sent the documents to the MEK (Hungarian Electronic Library) collection of National Széchényi Library. At present, our Library services 450 books from the stock of the Scientifical Library of the Haáz Rezső Museum.